For centuries, battering rams have been used to break down gates, walls and doors to force entrance. In ancient times, a battering ram was often nothing more than a heavy wooden beam which was repeatedly pounded by a large group of soldiers against city gates or walls to forcibly gain entrance.
In modern times, variations of the ancient battering ram are still used when circumstances require quick and efficient entrance, such as when a fire fighter must gain access to the interior of a burning building or a law enforcement official must break down a door to apprehend a criminal and/or obtain evidence before it can be destroyed. For example, U.S. Pat. No. 4,681,171 of Kee et al. discloses a battering ram operable by one person which includes a concrete-filled tube with an epoxy resin contact face. U.S. Pat. No. 5,067,237 of Holder discloses yet another type of battering ram which includes a pointed end with barbs to enable the door to be hooked and pulled outward. Sledge hammers have also been employed to achieve the same result.
However, most doors require many blows from such means before entry is achieved. Furthermore, such battering rams are often heavy, cumbersome and difficult to efficiently manipulate. The resultant delay in gaining entry is undesirable for both efficiency and safety reasons. For example, in the law enforcement context, speed and the element of surprise are essential to the safety of law enforcement personnel and the collection and recovery of evidence. Otherwise, while the officers are in the process of breaking down the door, the occupants may arm themselves, destroy evidence, escape, or even fire through the door at the officers attempting to break it down. Of primary importance is the avoidance of casualties. Accordingly, the door must be breached before any of the occupants realize what has happened.
The delay in breaking down the door when using prior art battering rams can be at least partially explained by considering the physics involved in breaking a door with a ram. The ram has a certain mass which is accelerated to a striking velocity by the individuals swinging it. The kinetic energy of the moving mass is applied to the door when the head of the ram contacts the door. Significantly, the force is not applied to the door all at once: the ram comes to a stop during a finite amount of time during which the energy transfer to the door occurs. In part, the speed of the ram determines the total force applied to the door; the speed of the energy transfer determines the peak force on the door. A higher peak force is more effective at breaking doors because for every door there is a threshold force required to begin the process of tearing and ripping that destroys the integrity of the door. Once the force applied is sufficient to start destroying the integrity of the door, it takes very little extra force to complete the job.
The peak force applied to the door is ultimately limited by the velocity with which the ram strikes the door. Increasing the impact velocity of the ram, for the same total energy, is more effective in breaking the door. To bring the total energy available to bear on the door in as short a time as possible requires a higher striking velocity. Thus, there is a need for an improved battering ram which can quickly and efficiently break down doors by providing a higher striking velocity to increase the peak force initially applied to the door.